The objectives of this project are to determine whether the observed age-related alteration of enzymes is due to a sequence change or to a post-synthetic modification. Enolase from young and old Turbatrix aceti, a free-living nematode, will be isolated and purified. Comparison will be made of the primary structure by analysis of peptides obtained after reaction of the protein with cyanogen bromide and from tryptic digests. Dissimilar peptides from the two enolase preparations, if found, will be investigated. A second suitable enzyme, perhaps phosphoglycerate kinase, alpha-amylase, fumarase, alcohol dehydrogenase or acid phosphatase will be purified from young and aging organisms and examined as above. To ascertain that the mechanism of formation of altered enzymes is a general one, phosphoglycerate kinase and enolase from young and old rats (liver, muscle) will be compared. The age at which inactive enzymes begin to accumulate in muscle and liver will be determined.